When you get the mission to destroy the large gun across the river from the Eiffel Tower, nearby on the same building is a smaller anti-aircraft gun. Kill all the guards nearby but leave the AA gun intact. Once the mission is completed, you can use the AA gun to shoot down Zeppelins. This will give you a level 5 alarm, which causes a series of airplanes to begin strafing you. Zeppelins earn $50 and planes $100 when shot down. The targets are unlimited, allowing you to get as much money as desired. Once you are done, jump off the building and die. When you return to HQ, you will have lost your weapons but have lots of money to replace them. You can repeat this as many times as desired as long as the last AA gun remains intact.

Easy races

Walk to the side of a car before a race begins. Aim your gun at the driver, and he will exit his car. Repeat this with all the other cars. Then, go back to your car, and you will be the only racer and can easily win.

Climbing buildings

When trying to climb up to a scenic point on top of a building, follow the glowing yellow lamps.

Defeating Nazis

Act suspiciously to lure a Nazi away from his post, then kill him when no one is around.

Race car locations

The Silver Dart, Aurora, Beta Romero, Beta Romero 12C, Delgado, Altair, Silver Claw, Drake, and Silver Claw Mk. II can be found at the following locations:

Tank and APC locations

The Flammwagen, Wulf, AR 33, Panther Mk. III, Half-track, and Foucalt can be found at the following locations:

Easy "Mad Bomber" perk

Steal a Nazi vehicle, and park it in your garage. Destroy it, then get a new one from the garage keeper. Destroy that one, and continue doing this until five of them have been destroyed to get the "Mad Bomber" perk.